CN111865353A - RF front end with reduced receiver desensitization - Google Patents
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
- H04B1/50—Circuits using different frequencies for the two directions of communication
- H04B1/52—Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa
- H04B1/525—Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa with means for reducing leakage of transmitter signal into the receiver
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
- H04B1/50—Circuits using different frequencies for the two directions of communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/26—Modifications of amplifiers to reduce influence of noise generated by amplifying elements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/12—Neutralising, balancing, or compensation arrangements
- H04B1/123—Neutralising, balancing, or compensation arrangements using adaptive balancing or compensation means
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
- H04B1/401—Circuits for selecting or indicating operating mode
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/02—Transmitters
- H04B1/04—Circuits
- H04B2001/0408—Circuits with power amplifiers
- H04B2001/0416—Circuits with power amplifiers having gain or transmission power control
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Abstract
An RF front end that reduces receiver desensitization is disclosed. Systems and methods for reducing receiver desensitization caused by coupling between a main antenna and a diversity antenna. More specifically, the system and method reduce receiver desensitization due to harmonic components associated with signals transmitted by a primary antenna falling within a frequency band in which a diversity antenna is configured to sense the signals. The system and method include: amplifying the first signal to generate a transmission signal for transmission via the main antenna; receiving a received signal at a diversity antenna; amplifying the reception signal via a low noise amplifier to apply a gain to the reception signal; inverting the phase of the transmission signal; and adding the inverted transmit signal to the amplified receive signal to produce a corrected receive signal. Thus, at the Radio Frequency (RF) front end, harmonic components introduced into the received signal are cancelled via negative feedback.
Description
Background
Many mobile devices include both primary and diversity antennas to support communication on each antenna, thereby improving the quality of communications to and from the mobile device. However, if the main and diversity antennas are located in close proximity to each other, the two antennas couple to each other, resulting in the signal transmitted by one antenna being sensed by the other antenna. Due to this coupling, communication at the other antenna is degraded (sometimes referred to as desensitized). Therefore, mobile device designers tend to physically separate the main antenna and the diversity antenna as much as possible to reduce coupling between the main antenna and the diversity antenna.
However, as mobile devices become smaller while including more components, it becomes increasingly difficult to physically separate the main antenna from the diversity antenna. Thus, while physical separation may separate the primary and secondary antennas to some extent, additional techniques are needed to mitigate the effects of coupling effects between the primary and diversity antennas.
Further, many communication systems now involve Carrier Aggregation (CA) techniques to improve communication throughput. CA may be implemented by Time Division Duplexing (TDD) using different time slots that separate the uplink and downlink into the same carrier (e.g., frequency) or by Frequency Division Duplexing (FDD) using different component carriers to transmit uplink and downlink signals simultaneously. Due to the synchronization characteristics of FDD communication and the above-mentioned coupling effect, the signal transmitted by the main antenna is sensed at the diversity antenna. In other words, the signal transmitted by the main antenna prevents the diversity antenna from correctly receiving other signals. It should be noted that this desensitization still occurs in TDD systems, although to a lesser extent than FDD systems.
Conventional solutions rely on filtering techniques that filter out the carrier associated with the main antenna. However, for some combinations of uplink and downlink carriers, harmonics associated with the uplink carrier (and/or intermodulation distortion harmonics associated with the composite CA transmit signal) fall within a frequency band that includes the downlink carrier associated with the diversity antenna. Thus, conventional filtering techniques cannot filter out harmonics associated with the uplink carrier, nor the downlink carrier associated with the diversity antenna.
Disclosure of Invention
In one embodiment, a system for reducing receiver desensitization is provided. The system comprises: a first communication circuit configured to transmit a signal at a first frequency band, the first communication circuit comprising (i) a power amplifier configured to apply a gain to a first signal to produce a transmit signal, and (ii) a first antenna configured to transmit the transmit signal. The system also includes a second communication circuit configured to receive signals at a second frequency band, the second communication circuit including (i) a second antenna configured to receive the received signals, wherein the transmit signals are transmitted while the second antenna receives the received signals, and (ii) a low noise amplifier configured to apply a gain to the received signals. In addition, the system includes: a feedback circuit operatively connected to the first communication circuit and configured to invert the transmit signal; and an adder operatively connected to the feedback circuit and the second communication circuit, the adder configured to add the inverted transmit signal to the amplified receive signal to produce a corrected receive signal.
In another embodiment, a method for reducing receiver desensitization is provided. The method comprises the following steps: (1) amplifying a first signal to produce a transmit signal for transmission via a first antenna, the first signal comprising a first component signal carried by a first component carrier within a first frequency band and a second component signal carried by a second component carrier within the first frequency band; (2) receiving a received signal at a second antenna configured to sense signals within a second frequency band, wherein harmonic frequencies associated with the first component carrier or the second component carrier fall within the second frequency band; (3) amplifying the reception signal via a low noise amplifier to apply a gain to the reception signal; (4) inverting the phase of the transmission signal; and (5) adding the inverted transmit signal to the amplified receive signal to produce a corrected receive signal.
In yet another embodiment, a system for reducing receiver cross-desensitization is provided. The system comprises: (1) a first transmit circuit configured to transmit a signal at a first frequency band, the transmit circuit comprising (i) a first power amplifier configured to apply a gain to the first signal to produce a first transmit signal, (ii) a first antenna configured to transmit the first transmit signal and receive a first receive signal, and (iii) a first duplexer configured to control whether the first antenna transmits the first transmit signal or receives the first receive signal; (2) a second transmit circuit configured to transmit signals at a second frequency band, the second transmit circuit comprising (i) a second power amplifier configured to apply a gain to a second signal to produce a second transmit signal, (ii) a second antenna configured to transmit the second transmit signal and receive a second receive signal, and (iii) a second duplexer configured to control whether the second antenna transmits the second transmit signal or receives the second receive signal; and (3) a hybrid receive circuit comprising (i) a non-linear amplifier configured to apply a gain of approximately one to an aggregate signal comprised of the first transmit signal and the second transmit signal, wherein the non-linear characteristic of the non-linear amplifier approximates the non-linear characteristic of the first duplexer and/or the second duplexer, (ii) a phase shifter configured to shift the phase of the output of the non-linear amplifier by 180 degrees to produce an inverted feedback signal, (iii) a first adder configured to add the inverted feedback signal to the first receive signal to produce a first corrected receive signal, and (iv) a second adder configured to add the inverted feedback signal to the second receive signal to produce a second corrected receive signal.
Drawings
Fig. 1 is a diagram depicting an exemplary scenario in which a primary antenna causes receiver desensitization at a diversity antenna;
FIG. 2 depicts an exemplary circuit diagram for reducing desensitization of a diversity antenna caused by a main antenna;
3A-3D depict exemplary signals at different locations of the exemplary circuit of FIG. 2;
fig. 4 depicts an exemplary circuit diagram for reducing cross-desensitization when diversity antennas are adapted to support uplink communications; and
fig. 5 illustrates an example method in which circuitry of a user equipment is configured to reduce receiver desensitization caused by simultaneously transmitting and receiving signals at a radio frequency front end including a first antenna and a second antenna.
Detailed Description
Fig. 1 depicts an exemplary scenario in which a primary antenna causes receiver desensitization at a diversity antenna. As shown, the transmit signals include a first component signal 62 transmitted using a component carrier centered at frequency CC1 and a second component signal 64 transmitted using a second component carrier centered at frequency CC 2. Thus, the transmit circuitry includes a transmit filter (as shown by curve 60) configured to allow signals 62 and 64 to pass. It should be appreciated that signals 62 and 64 are not ideal stubs due to non-linear characteristics associated with various components of the corresponding transmit circuitry (such as power amplifiers, duplexers, etc.).
As described below, the non-linear characteristics of the components used to generate signals 62 and 64 cause intermodulation harmonics to appear in the transmitted signal. More specifically, the composite transmit signal comprising signals 62 and 64 is generated such that third order intermodulation harmonics occur at frequencies IM 3-and IM3+, and fifth order intermodulation frequencies occur at frequencies IM 5-and IM5 +. However, in the illustrated scenario, the diversity antenna is configured to sense received signals in a frequency band that includes frequencies IM3+ and IM5+ where third and fifth order intermodulation occurs. For example, transmitting the composite transmit signal at band 71(617MHz-698 MHz) may result in the presence of third order intermodulation harmonics within the PCS band (1850MHz-1990 MHz). Similarly, transmitting the composite transmit signal at band 17(704 MHz-716 MHz) may result in the presence of third order intermodulation harmonics within the band 4 downlink spectrum (2110MHz-2155 MHz). It should be understood that the presently disclosed techniques may be applied to any combination of frequency bands in which intermodulation harmonics occur within the frequency range of interest. Thus, conventional methods of implementing low-pass or band-pass filters to filter out harmonic products (including intermodulation harmonics) cannot be applied without filtering the intended received signal.
Fig. 2 depicts a circuit diagram of an exemplary circuit 100 configured to reduce desensitization of the diversity antenna 126 caused by the primary antenna 116. In the exemplary circuit 100, the diversity antenna 126 is used in a receive-only mode. In most communication systems, the carrier frequency supporting uplink communications via the circuit 100 is a lower frequency carrier than the carrier frequency supporting downlink communications at the circuit 100. The example circuit 100 may be implemented within a User Equipment (UE) that supports inter-band carrier aggregation technology, such as a mobile phone, a tablet, a smart watch, a laptop, a mobile access point, an internet of things (IoT) device, and/or any other computing device. In particular, the circuit 100 may be implemented in a UE configured to implement inter-band carrier aggregation, wherein a frequency band for an uplink carrier includes harmonic products that occur in a frequency band that includes a downlink carrier.
As shown, the exemplary circuit 100 is a Radio Frequency (RF) front end circuit communicatively coupled to a modem 103, the modem 103 configured to convert analog signals received via the RF front end for processing by one or more baseband components. Similarly, modem 103 is configured to convert digital signals generated by one or more baseband components to analog signals for transmission by the RF front end. For example, modem 103 may be configured to generate signal 105 for transmission by an RF front end. For ease of illustration, signal 105 is shown as a two tone signal, where each tone represents a different carrier. It should be appreciated that in many embodiments, signal 105 may be encoded according to any known modulation scheme (e.g., QPSK or QAM) and any associated bandwidth (e.g., 1.4MHz, 3MHz, 5Hz, 10MHz, 15MHz, 20MHz, etc., up to a maximum bandwidth per carrier allowed by the implemented communication protocol). In some embodiments, the signals carried by the component carriers are encoded according to different communication protocols. For example, signals carried by a first carrier may be encoded according to a Long Term Evolution (LTE) protocol, and signals carried by a second carrier may be encoded according to a New Radio (NR)/5G protocol. In these embodiments, the carrier aggregation technique may be referred to as dual connectivity.
The exemplary circuit 100 includes four main components: a first communication circuit 110 configured to transmit a transmit signal via a primary antenna 116; a second communication circuit 120 configured to sense a signal at a diversity antenna 126; a feedback circuit 130 configured to invert the signal 105; and an adder 140 configured to add the output of the feedback circuit 130 to the output of the second communication circuit 120.
Starting with the first communication circuit 110, the signal 105 passes through a power amplifier 112, the power amplifier 112 being configured to apply a gain to the signal 105 to produce a transmit signal. In the exemplary circuit 100, the power amplifier 112 is configured to apply gain to all uplink carriers. The particular gain applied to the signal 105 may vary depending on network conditions and/or how much transmit power is required by a base station, such as an evolved node b (enb) or next generation node b (gnb), to detect the signal produced by the primary antenna 116.
It should be understood that the power amplifier 112 is not an ideal linear amplifier. Thus, the nonlinear characteristics of power amplifier 112 introduce intermodulation harmonics into signal 105. Referring also to fig. 3A, shown is an exemplary diagram depicting a resulting transmit signal 300 generated by the power amplifier 112. The transmitted signal 300 is still comprised in the carrier frequency f 1And f2Two tones at each of the two tones. However, intermodulation harmonics are also generated at the carrier frequency f1And f2The central first order harmonic. Furthermore, at a frequency 2f1And 2f2And a frequency 3f1And 3f2Respectively, there are second order and third order intermodulation harmonics in the transmitted signal 300. For ease of illustration, higher order harmonics and pairs of lower frequency harmonics are not depicted in fig. 3A.
As shown, the first communication circuit 110 routes the output of the power amplifier 112 (e.g., the transmit signal 300) through a low pass filter 115, the low pass filter 115 configured to filter out higher frequency downlink carriers. The output of the low pass filter 115 is routed to a duplexer (or switch) 114, the duplexer (or switch) 114 being configured to control whether the main antenna 116 operates in a transmit mode or a receive mode. When the primary antenna 116 is operating in a transmit mode, the primary antenna 116 is configured to transmit the filtered transmit signal 300. Conversely, when main antenna 116 is operating in a receive mode, the received signal is routed to a high pass filter 117 configured to filter out lower frequency uplink carriers and then to a low noise amplifier 113 configured to apply gain to the received signal for improved processing by modem 103 and/or baseband components associated therewith.
As described herein, the filtered transmit signal 300 is sensed at the diversity antenna 126 due to the coupling between the primary antenna 116 and the secondary antenna 126. The received signal (i.e., the signal carried by the higher frequency downlink carrier and the sensed transmitted signal 300) is routed to a high pass filter 124 configured to filter out the lower frequency uplink carrier. The output of the filter 124 is then routed to the low noise amplifier 122 to increase the gain of the received signal for improved processing at baseband.
Referring also to fig. 3B, shown is an exemplary diagram depicting filtered received signal 325 produced by filter 124. For ease of illustration, filtered received signal 325 includes only intermodulation harmonics and does not include the intended received signal. Because filter 124 is configured to filter out the uplink carrier frequency, at carrier frequency f1And f2The portion of the transmit signal 300 that is centered has been appropriately filtered. However, because of the frequency 2f1And 2f2And/or frequency 3f1And 3f2Falls within the frequency band that includes the downlink carrier so intermodulation harmonics are still present in the filtered received signal 325. Thus, the signal-to-noise ratio of the downlink carrier is reduced, reducing downlink connectivity at the UE.
While conventional solutions may attempt to correct for these intermodulation harmonics at baseband, doing so requires a priori knowledge of the particular uplink and downlink carriers used for communication. Based on this knowledge, the baseband signal can be modified to reduce the effects of these harmonics. However, many communication systems dynamically shift the particular carriers used in uplink and downlink communications. Therefore, there is a need to continually adjust these baseband techniques, reducing the ability of the UE to adapt to changing network conditions. In contrast, the techniques disclosed herein filter out intermodulation harmonics at the RF front-end. By utilizing the disclosed techniques, intermodulation harmonics can be filtered out of received signal 325 without retuning baseband components, regardless of the particular frequencies used for the uplink and downlink carriers.
To implement the RF front-end filtering technique, the example circuit 100 includes a feedback circuit 130, the feedback circuit 130 configured to invert the signal transmitted by the main antenna 116 to cancel a corresponding signal sensed at the diversity antenna 126 due to the aforementioned coupling therebetween. As described above, the signal sensed at diversity antenna 126 is not routed directly to modem 103, but rather passes through high pass filter 124 and low noise amplifier 122 configured to filter out the lower frequency uplink carrier to apply gain to the received signal for improved baseband processing. Thus, the feedback circuit 130 is configured to take these components into account when inverting the transmit signal 300.
The exemplary feedback circuit 130 includes a high pass filter 134 configured to filter out lower frequency uplink carriers. Thus, the output of filter 134 is similar to received signal 325. In addition, the feedback circuit includes an amplifier 132. It should be understood that amplifier 122 is not an ideal amplifier and includes non-linear characteristics. Thus, amplifier 132 is configured to subject the output of filter 134 to a non-linear characteristic similar to that introduced into received signal 325 by low noise amplifier 122. In some embodiments, because the signal carried by the feedback circuit 130 is not subject to free space attenuation, the amplifier 132 is configured to apply a gain (i.e., the amplifier is not configured to actually amplify the signal). In these embodiments, the amplifier 132 is configured to modify the feedback signal to approximate the non-linear characteristic of the amplifier 122 without adjusting the power level of the feedback signal.
In addition, the feedback circuit 130 includes a phase shifter 136 configured to invert the output of the amplifier 132. More specifically, the phase shifter 136 is configured to shift the phase of the output of the amplifier 132 by 180 degrees. Referring also to fig. 3C, shown is an exemplary diagram depicting the resulting inverted transmit signal 350 produced by the phase shifter 136. As shown, inverted transmit signal 350 includes inverted versions of the second order intermodulation products and the third order intermodulation products included in transmit signal 300 and/or receive signal 325. While the exemplary circuit 100 couples the first communication circuit 110 to the feedback circuit 130 at the output node of the power amplifier 112, in an alternative embodiment, the first communication circuit 130 is coupled to the feedback circuit 130 at the output node of the duplexer 114 to account for the non-linear characteristics of the duplexer 114.
The exemplary circuit 100 also includes an adder 140, the adder 140 configured to add the output of the feedback circuit 130 to the output of the second communication circuit 120. For example, summer 140 may add inverted transmit signal 350 to filtered receive signal 325. Thus, intermodulation harmonic interference introduced by the nonlinear components of the first communication circuit is subtracted from the signal sensed by the diversity antenna 126, thereby increasing the signal-to-noise ratio and reducing receiver desensitization. The output of the adder 140 is routed to the modem 103 for baseband processing.
Referring also to fig. 3D, shown is an exemplary diagram depicting a corrected received signal 375 produced by adder 140. For ease of illustration, corrected receive signal 375 includes only intermodulation harmonics and does not include the intended receive signal. As shown in fig. 3D, the feedback circuit 130 may not completely cancel the intermodulation harmonics. For example, free space attenuation between the main receiver 116 and the diversity antenna 126 and/or the low noise amplifier 122 may change the power level associated with intermodulation harmonics. Thus, the power level of the intermodulation harmonics in the signal generated by amplifier 132 may not match the power level of the intermodulation harmonics in the signal generated by amplifier 122. Notwithstanding these differences, the disclosed techniques are able to mitigate a significant portion of intermodulation harmonic interference and provide a meaningful improvement in the quality of the signals detected at diversity antenna 126.
In the exemplary circuit 100, the power amplifier 112 and the low noise amplifier 122 are configured to amplify an aggregated signal composed of various component carriers. In alternative embodiments, such as embodiments implementing dual connectivity, each uplink carrier may be amplified by a respective power amplifier 112. Similarly, in these embodiments, each downlink carrier may be amplified by a respective low noise amplifier 122. In these embodiments, the feedback circuits 130 may include respective amplifiers 132, the amplifiers 132 being configured to subject the output signals to respective non-linear characteristics of the respective low noise amplifiers 122. Thus, in these embodiments, the circuit 100 includes respective adders configured to add inverted outputs of the respective amplifiers 132 to respective outputs of the low noise amplifiers 122.
Because diversity antenna 126 is configured to operate in a receive-only mode, there is no transmitted signal for primary antenna 116 to sense. Thus, there is no need to reduce intermodulation harmonic interference at the main antenna 116. That is, the techniques described with respect to example 100 may be extended to diversity antennas configured to transmit signals while also maintaining an implementation of receive diversity.
Referring now to fig. 4, illustrated is an exemplary circuit 200 configured to reduce cross-interference between a main antenna 216 and a diversity antenna 226. The example circuitry 200 may be implemented within a UE that supports inter-band carrier aggregation techniques. In some embodiments, the primary antenna 216 may be configured to transmit and/or receive signals using carriers within a first frequency band, and the diversity antenna 226 may be configured to transmit and/or receive signals using carriers within a second frequency band. According to some aspects, the first frequency band is associated with harmonic frequencies occurring within the second frequency band, and vice versa. Thus, the exemplary circuit 200 is generally configured to reduce intermodulation harmonics sensed by each of the main antenna 216 and the diversity antenna 226.
As shown, the exemplary circuit 200 is a Radio Frequency (RF) front end circuit communicatively coupled to a modem 203, the modem 203 configured to convert analog signals received via the Radio Frequency (RF) front end for processing by one or more baseband components. Similarly, modem 203 is configured to convert digital signals generated by one or more baseband components to analog signals for transmission by the RF front end. For example, modem 203 may be configured to generate a first signal for transmission via primary antenna 216 and a second signal for transmission via secondary antenna 226. The first and second signals may be encoded according to any known modulation scheme (e.g., QPSK or QAM) and any associated bandwidth (e.g., 1.4MHz, 3MHz, 5Hz, 10MHz, 15MHz, 20MHz, etc., up to a maximum bandwidth per carrier allowed by the implemented communication protocol). In some embodiments, the first signal and the second signal are encoded according to different communication protocols. For example, the first signal may be encoded according to a Long Term Evolution (LTE) protocol and the second signal may be encoded according to a New Radio (NR) protocol.
The exemplary circuit 200 includes three main components: a first transmit circuit 210 configured to transmit signals within a first frequency band via a primary antenna 216; a second transmit circuit 220 configured to transmit signals within a second frequency band via a diversity antenna 226; and hybrid receive circuitry 230 configured to mitigate cross-interference introduced by coupling between the main antenna 216 and the diversity antenna 226.
Starting with the first transmit circuit 210, the first signal generated by the modem 203 passes through a power amplifier 212, the power amplifier 212 configured to apply a gain to the first signal to generate a first transmit signal. In the exemplary circuit 200, the power amplifier 212 is configured to apply a gain to all uplink carriers in the first frequency band. However, in other embodiments, each uplink carrier may pass through a respective power amplifier 212. The particular gain applied to the first signal (and/or the particular uplink carrier) may vary depending on network conditions and/or how much transmit power is required by a base station (e.g., evolved node b (enb) or next generation node b (gnb)) to detect the signal generated by the primary antenna 216. As described herein, power amplifier 212 is not an ideal linear amplifier, resulting in intermodulation harmonics appearing within the first transmit signal.
The first transmit circuit 210 then routes the output of the power amplifier 212 to a low pass filter 215 to filter out the higher frequency downlink carrier within the first frequency band. The output of the low pass filter 215 is routed to a duplexer (or switch) 214, the duplexer (or switch) 214 being configured to control whether the primary antenna 216 operates in a transmit mode or a receive mode. When the primary antenna 216 operates in a transmit mode, the primary antenna 216 is configured to transmit the filtered first transmit signal. Conversely, when the primary antenna 216 is operating in a receive mode, the first receive signal is routed to the hybrid receive circuit 230.
Similarly, the second transmit circuit 220 routes the second signal generated by the modem 203 through the power amplifier 222, the power amplifier 222 configured to apply a gain to the second signal to generate a second transmit signal. In the exemplary circuit 200, the power amplifier 222 is configured to apply a gain to all uplink carriers in the second frequency band. However, in other embodiments, each uplink carrier may pass through a respective power amplifier 222. The particular gain applied to the second signal (and/or the particular uplink carrier) may vary depending on network conditions and/or how much transmit power is required by a base station (such as an evolved node b (enb) or next generation node b (gnb)) to detect the signal generated by the diversity antenna 226. As described herein, power amplifier 222 is not an ideal linear amplifier, resulting in intermodulation harmonics appearing within the second transmit signal.
The second transmit circuit 220 then routes the output of the power amplifier 222 to a low pass filter 225 to filter out the higher frequency downlink carrier within the second frequency band. The output of the low pass filter 225 is routed to a duplexer (or switch) 224, the duplexer (or switch) 224 being configured to control whether the diversity antenna 226 operates in a transmit mode or a receive mode. The diversity antenna 226 is configured to transmit the filtered second transmit signal when the diversity antenna 226 is operating in a transmit mode. Conversely, when the diversity antenna 226 operates in a receive mode, the second receive signal is routed to the hybrid receive circuit 230.
Turning to the hybrid receive circuit 230, the first and second receive signals are routed through respective high pass filters 231a and 231b, the high pass filters 231a and 231b configured to filter out lower frequency uplink carrier frequencies within the first and second frequency bands, respectively. In addition, the hybrid receive circuit 230 is configured to obtain the first transmit signal and the second transmit signal as feedback signals for mitigating the effects of intermodulation harmonic interference. Thus, the first transmit signal is routed through a high pass filter 233a configured to filter out lower frequency uplink carriers within the second frequency band, and the second transmit signal is routed through a high pass filter 233b configured to filter out lower frequency uplink carriers within the first frequency band.
The outputs from the high pass filters 233a and 233b are aggregated and routed through a nonlinear amplifier 234, the nonlinear amplifier 234 configured to apply a gain (such as a gain of approximately one) to the aggregated signal. The nonlinear amplifier 234 is further configured to subject the aggregate signal to nonlinear characteristics similar to the nonlinear characteristics introduced into the transmit and/or receive signals by the duplexers 214 and/or 224 to generate a feedback signal indicative of (i) intermodulation harmonics introduced into the second receive signal from the first transmit signal transmitted by the primary antenna 216 and (ii) intermodulation harmonics introduced into the first receive signal from the second transmit signal transmitted by the diversity antenna 226. The feedback signal is routed to a phase shifter 235, and the phase shifter 235 is configured to shift the phase of the output of the non-linear amplifier 234 by 180 degrees to produce an inverted feedback signal. Accordingly, the inverted feedback signal at the output of phase shifter 235 includes a signal configured to cancel intermodulation harmonic signals sensed by main antenna 216 and diversity antenna 226 due to coupling between main antenna 216 and diversity antenna 226.
The hybrid receiving circuit 230 further includes adders 237a and 237b configured to add the inverted feedback signal to the received signal. More specifically, the hybrid receiving circuit 230 includes an adder 237a configured to add the inverted feedback signal to the filtered first received signal, and an adder 237b configured to add the inverted feedback signal to the filtered second received signal. The outputs of the adders 237a and 237b are routed to respective low noise amplifiers 239a and 239b, the low noise amplifiers 239a and 239b being configured to amplify the respective outputs for improved processing by the modem 203 at baseband. Therefore, the intermodulation harmonics in the output of the low noise amplifier 239a and the intermodulation harmonics in the output of the low noise amplifier 239b are attenuated.
Fig. 5 illustrates an exemplary method 500 in which circuitry (e.g., circuitry 100) of a UE is configured to reduce receiver desensitization introduced by simultaneous transmission and reception of signals at an RF front end, the RF front end including a first antenna and a secondary antenna. More specifically, the method 500 is configured to reduce harmonic interference when a frequency band for transmitting signals via a first antenna is associated with a harmonic frequency within a frequency band for receiving signals at a second antenna.
The method 500 may begin at block 502 when circuitry amplifies a first signal to produce a transmit signal for transmission via a first antenna (e.g., a primary antenna). The first signal may be generated by a modem (e.g., modem 103) using a carrier aggregation technique such that the first signal includes a first component signal carried by a first component carrier and a second component signal carried by a second component carrier, both of which are within a first frequency band. In some embodiments, the modem encodes the first component signal according to an LTE protocol and the second component signal according to an NR protocol.
The circuit may include a power amplifier (e.g., power amplifier 112) configured to amplify the first signal. In some embodiments, the circuit includes a single amplifier configured to amplify each of the component carriers within the first signal. In other embodiments, the first component signal is amplified by a first amplifier and the second component signal is amplified by a second amplifier. It will be appreciated that due to the non-linear nature of the amplifier, the transmitted signal includes harmonic components that lie outside the first frequency band (e.g., within the second frequency band).
At block 504, the circuit is configured to receive a received signal at a second antenna (e.g., a diversity antenna). More specifically, the second antenna is configured to sense signals transmitted within a second frequency band. As described above, the transmit signal is included in the sensed receive signal due to coupling with the primary antenna. Thus, the sensed received signal includes harmonic components within the spectrum of interest of the received signal. Thus, although the circuit is configured to filter the received signal using a high pass filter configured to filter out the uplink carrier, harmonic components of the transmitted signal are still present in the received signal after the filter is applied.
At block 506, the circuit is configured to amplify the receive signal via a low noise amplifier (e.g., low noise amplifier 122) to apply a gain to the receive signal. In some embodiments, the circuit is configured to amplify the filtered received signal. In other embodiments, the circuit amplifies the received signal prior to filtering the received signal. Additionally, in some embodiments, the circuit includes a single amplifier configured to amplify each of the component carriers within the received signal. In other embodiments, the first component received signal is amplified by a first amplifier and the second component received signal is amplified by a second amplifier.
At block 508, the circuit is configured to invert the transmit signal to produce negative feedback to cancel harmonic components included in the filtered receive signal. Thus, inverting the transmit signal may include: the lower frequency first and second component uplink carriers within the first frequency band are filtered and the non-linear characteristics of the low noise amplifier 122 and/or any other non-linear components in the RF front end receive path (e.g., components included in the second communication circuit 120) are applied to the filtered transmit signal via a non-linear amplifier (e.g., amplifier 132). In some embodiments, the non-linear amplifier applies a non-linear characteristic of the RF front end to each of the component signals of the filtered transmit signal. In other embodiments, the first non-linear amplifier applies the non-linear characteristic applied to the first component downlink carrier in the receive path to the first component signal of the filtered transmit signal, and the second non-linear amplifier applies the non-linear characteristic applied to the second component downlink carrier in the receive path to the second component signal of the filtered transmit signal. In any case, the circuit is configured to shift the phase of the output of the non-linear amplifier by 180 degrees.
At block 510, the circuit is configured to add the inverted transmit signal to the amplified receive signal to produce a corrected receive signal. The inverted transmit signal is at substantially the same frequency as the harmonic component because the inverted transmit signal experiences the same non-linear characteristics as the harmonic component of the transmit signal sensed at the second antenna due to coupling. In embodiments where the respective carriers are individually amplified, the circuit may be configured to add the inverted output of the first non-linear amplifier to the first component received signal to produce a first corrected received signal and to add the inverted output of the second non-linear amplifier to the second component received signal to produce a second corrected received signal. The circuitry may then route the corrected received signal to a modem for baseband processing.
It will also be understood that, unless the phrase "as used herein is used in this patent, the term '____' is hereby defined to mean … …" or a similar phrase explicitly defining the term, it is not intended to be expressly or implicitly limited to its literal or ordinary meaning, and that the term should not be construed as being limited in scope based on any statement made in any part of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this disclosure is referred to in this disclosure in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term by limited, by implication or otherwise, to that single meaning. Finally, unless a claim element is defined by reciting the word "means" and a function without reciting any structure, it is not intended that the scope of any claim element be construed based on the application of 35u.s.c. § 112 (f).
Throughout this specification, multiple instances may implement a component, an operation, or a structure described as a single instance. While various operations of one or more methods are shown and described as separate operations, one or more of the individual operations may be performed concurrently, and some operations may be performed in a different order than that shown. Structures and component functions presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and component functions presented as a single component can be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.
For example, other architectures can be used to implement the described functionality and these are intended to be within the scope of the present disclosure. To this end, while the present disclosure generally describes the transmit path of the RF front end as utilizing a power amplifier to amplify the signal and the receive path of the radio frequency front end as utilizing a low noise amplifier, in some embodiments, alternative types of amplifiers may be implemented in the transmit and/or receive paths. As another example, the present disclosure relates to high pass filters and low pass filters; however, in some embodiments, the high pass filter or the low pass filter may be implemented as a band pass filter. Further, while a particular allocation of responsibility is defined above for purposes of discussion, the various functions and responsibilities may be allocated and divided in different ways depending on the particular situation.
The detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this application. After reading this disclosure, one of ordinary skill in the art will understand additional alternative structural and functional designs through the principles disclosed herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes, and variations apparent to those skilled in the art may be made in the arrangement, operation, and details of the methods and apparatus disclosed herein without departing from the spirit and scope as defined in the appended claims.
Claims (20)
1. A radio frequency, RF, front-end circuit for reducing receiver desensitization, the RF front-end circuit comprising:
a first communication circuit configured to transmit a signal at a first frequency band, the first communication circuit comprising:
a power amplifier configured to apply a gain to the first signal to generate a transmit signal, an
A first antenna configured to transmit the transmission signal; a second communication circuit configured to receive signals at a second frequency band, the second communication circuit comprising:
a second antenna configured to receive a reception signal, wherein the transmission signal is transmitted while the second antenna receives the reception signal, an
A low noise amplifier configured to apply a gain to the reception signal;
a feedback circuit operatively connected to the first communication circuit and configured to invert the transmit signal; and
an adder operatively connected to the feedback circuit and the second communication circuit, the adder configured to add the inverted transmit signal to the amplified receive signal to produce a corrected receive signal.
2. The RF front-end circuit of claim 1, wherein the transmit signal is transmitted using two or more component carriers located within the first frequency band and comprises one or more harmonic signals located at one or more respective harmonic frequencies outside the first frequency band.
3. The RF front-end circuit of claim 2, wherein the feedback circuit comprises:
A filter configured to filter out the component carrier of the transmit signal while allowing the one or more respective harmonic frequencies;
an amplifier configured to apply a gain of approximately one to an output of the filter, wherein a non-linear characteristic of the amplifier is substantially the same as a non-linear characteristic of the low noise amplifier; and
a phase shifter configured to shift a phase of an output of the amplifier by 180 degrees.
4. The RF front-end circuit of claim 2, wherein the second communication circuit comprises:
a filter configured to filter out the component carrier of the transmit signal from the receive signal.
5. The RF front-end circuit of claim 2, wherein the first signal comprises a first component signal carried by a first component carrier of the two or more component carriers and a second component signal carried by a second component carrier of the two or more component carriers.
6. The RF front-end circuit of claim 5, wherein the first component signal is encoded according to a first communication protocol and the second component signal is encoded according to a second communication protocol.
7. The RF front-end circuit of claim 6, wherein the first communication protocol is a Long Term Evolution (LTE) protocol and the second communication protocol is a New Radio (NR) protocol.
8. The RF front-end circuit of claim 5, wherein the first and second component signals comprise harmonic frequencies located in the second frequency band.
9. The RF front-end circuit of claim 5, wherein:
the power amplifier is a first power amplifier configured to amplify the first component signal to generate a first transmit signal; and is
The first communication circuit includes:
a second power amplifier configured to amplify the second component signal to generate a second transmit signal, an
A summer configured to combine the first transmit signal and the second transmit signal to generate the transmit signal.
10. The RF front-end circuit of claim 5, wherein:
the received signal is received using two or more component carriers located within the second frequency band;
the low noise amplifier is a first low noise amplifier configured to apply a gain to a first component carrier of the two or more component carriers within the second frequency band;
The second communication circuit comprises a second low noise amplifier configured to apply a gain to a second component carrier of the two or more component carriers within the second frequency band; and is
The feedback circuit includes:
a first amplifier configured to apply a gain of approximately one to a portion of the transmit signal located at the first component carrier of the two or more component carriers within the second frequency band, wherein a non-linear characteristic of the first amplifier is substantially the same as a non-linear characteristic of the first low noise amplifier; and
a second amplifier configured to apply a gain of approximately one to a portion of the transmit signal located at the second component carrier of the two or more component carriers within the second frequency band, wherein a non-linear characteristic of the second amplifier is substantially the same as a non-linear characteristic of the second low noise amplifier.
11. The system of claim 10, wherein:
the adder is a first adder configured to add an inverted output of the first amplifier to an output of the first low noise amplifier to produce a first corrected receive signal; and is
The system includes a second adder configured to add an inverted output of the second amplifier to an output of the second low noise amplifier to produce a second corrected receive signal.
12. A method implemented at a radio frequency, RF, front end circuit for reducing receiver desensitization, the method comprising:
amplifying a first signal to produce a transmit signal for transmission via a first antenna, the first signal comprising a first component signal carried by a first component carrier within a first frequency band and a second component signal carried by a second component carrier within the first frequency band;
receiving a received signal at a second antenna configured to sense signals within a second frequency band, wherein harmonic frequencies associated with the first component carrier or the second component carrier fall within the second frequency band;
amplifying the receive signal via a low noise amplifier to apply a gain to the receive signal;
inverting the transmit signal; and
the inverted transmit signal is added to the amplified receive signal to produce a corrected receive signal.
13. The method of claim 12, wherein inverting the transmit signal comprises:
Filtering the first component carrier and the second component carrier within the first frequency band;
applying, via a non-linear amplifier, a non-linear characteristic of the low noise amplifier to the filtered transmit signal; and
the phase of the output of the non-linear amplifier is shifted by 180 degrees via a phase shifter.
14. The method of claim 12, wherein the first component signal is encoded according to a long term evolution, LTE, protocol and the second component signal is encoded according to a new radio, NR, protocol.
15. The method of claim 12, wherein amplifying the first signal comprises:
amplifying the first component signal via a first power amplifier to generate a first transmit signal; and
amplifying the second component signal via a second power amplifier to generate a second transmit signal.
16. The method of claim 12, wherein:
the received signal is received using two or more component carriers located within the second frequency band;
the low noise amplifier is a first low noise amplifier; and is
Amplifying the received signal comprises:
amplifying a first component carrier of the two or more component carriers of the receive signal via the first low noise amplifier to produce a first component receive signal; and
Amplifying a second component carrier of the two or more component carriers of the receive signal via a second low noise amplifier to produce a second component receive signal.
17. The method of claim 16, wherein:
the non-linear amplifier is a first non-linear amplifier; and is
Inverting the transmit signal comprises:
applying, via the first non-linear amplifier, non-linear characteristics of the first low noise amplifier to a portion of the transmit signal located at the first component carrier of the two or more component carriers within the second frequency band; and
applying, via a second non-linear amplifier, non-linear characteristics of the second low noise amplifier to a portion of the transmit signal located at the second component carrier of the two or more component carriers within the second frequency band.
18. The method of claim 17, wherein adding the inverted transmit signal to the receive signal comprises:
adding an inverted output of the first non-linear amplifier to the first component receive signal to produce a first corrected receive signal; and
adding the inverted output of the second non-linear amplifier to the second component receive signal to produce a second corrected receive signal.
19. A Radio Frequency (RF) front-end circuit for reducing receiver cross-desensitization, the RF front-end circuit comprising:
a first transmit circuit configured to transmit a signal at a first frequency band, the first transmit circuit comprising:
a first power amplifier configured to apply a gain to a first signal to generate a first transmit signal,
a first antenna configured to transmit the first transmission signal and receive a first reception signal, an
A first duplexer configured to control whether the first antenna transmits the first transmission signal or receives the first reception signal;
a second transmit circuit configured to transmit signals at a second frequency band, the second transmit circuit comprising:
a second power amplifier configured to apply a gain to a second signal to generate a second transmit signal,
a second antenna configured to transmit the second transmission signal and receive a second reception signal, an
A second duplexer configured to control whether the second antenna transmits the second transmission signal or receives the second reception signal; and
a hybrid receive circuit, comprising:
a non-linear amplifier configured to apply a gain of approximately one to an aggregate signal composed of the first transmit signal and the second transmit signal, wherein a non-linear characteristic of the non-linear amplifier approximates a non-linear characteristic of the first duplexer and/or the second duplexer;
A phase shifter configured to shift a phase of an output of the non-linear amplifier by 180 degrees to generate an inverted feedback signal;
a first adder configured to add the inverted feedback signal to the first receive signal to produce a first corrected receive signal; and
a second adder configured to add the inverted feedback signal to the second receive signal to produce a second corrected receive signal.
20. The RF front-end circuit of claim 19, wherein the first signal is encoded according to a long term evolution, LTE, protocol and the second signal is encoded according to a new radio, NR, protocol.
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| US16/399,322 | 2019-04-30 | ||
| US16/399,322 US10749565B1 (en) | 2019-04-30 | 2019-04-30 | RF front end reduction of receiver de-sensitivity |
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| US10855325B2 (en) | 2018-08-21 | 2020-12-01 | Skyworks Solutions, Inc. | Discrete time cancellation for providing coexistence in radio frequency communication systems |
| US10840958B2 (en) | 2018-08-21 | 2020-11-17 | Skyworks Solutions, Inc. | Radio frequency communication systems with discrete time cancellation for coexistence management |
| US10840957B2 (en) | 2018-08-21 | 2020-11-17 | Skyworks Solutions, Inc. | Radio frequency communication systems with coexistence management based on digital observation data |
| US11558079B2 (en) | 2019-01-15 | 2023-01-17 | Skyworks Solutions, Inc. | Radio frequency communication systems with interference cancellation for coexistence |
| AU2020343678A1 (en) * | 2019-09-06 | 2022-04-21 | Nextivity, Inc. | Hybrid radio frequency combining system with signal cancellation |
| WO2021061834A1 (en) * | 2019-09-27 | 2021-04-01 | Skyworks Solutions, Inc. | Antenna-plexer for interference cancellation |
| WO2021061792A1 (en) | 2019-09-27 | 2021-04-01 | Skyworks Solutions, Inc. | Mixed signal low noise interference cancellation |
| CN112532271A (en) * | 2020-12-07 | 2021-03-19 | 维沃移动通信有限公司 | Radio frequency circuit and electronic device |
| CN114650073B (en) * | 2022-04-15 | 2023-05-16 | 成都信息工程大学 | Linearization correction method and device for radio frequency receiver |
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| EP3734846A1 (en) | 2020-11-04 |
| US10749565B1 (en) | 2020-08-18 |
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